ios - 解决两个平移手势识别器之间的冲突

Question

我有以下层次结构:

• 查看
  • subview

每个 View 都分配有 UIPanGestureRecognizer。外部平移手势识别器只对垂直平移感兴趣，因此我为此实现了委托(delegate)方法:

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)panGestureRecognizer {
    CGPoint velocity = [panGestureRecognizer velocityInView:panGestureRecognizer.view];
    return fabs(velocity.y) > fabs(velocity.x);
}

然而，Subview 的平移手势总是优先于识别。有没有办法让外部平移手势识别器先识别，如果失败， subview 中的平移手势可以接管？

我尝试同时识别并且它有效，但随后两个识别器开始平移:

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer 

    shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
        return YES;
    }

Answer 1

从 iOS 7 开始，UIGestureRecognizerDelegate Protocol 已经声明了两个委托(delegate)方法来满足你的需要，你可以使用 |gestureRecognizer:shouldRequireFailureOfGestureRecognizer:| 要么 |gestureRecognizerShouldBegin:shouldBeRequiredToFailByGestureRecognizer:|但以相反的方式。

以下片段是我的 UIPanGestureRecognizer 委托(delegate)实现:

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)panGestureRecognizer {
    CGPoint velocity = [panGestureRecognizer velocityInView:panGestureRecognizer.view];
    return fabs(velocity.y) > fabs(velocity.x);
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
    if (otherGestureRecognizer == panGestureOfSubView) {
        return YES;
    }

    return NO;
}